Can springboot dependency class can autowire service module?

Question

Can I call a class in parent module from dependency module in spring boot.Say I have a project A springboot application and project B is dependency (common module ) .I am able to Autowire and use classes of B from A . But the vice versa is not happening. B is dependency so no yml is configured nor version is given .When I try to say Autowire aclass it gives me nulll.

can you give a more concrete example of what you want to do? In general it is a bad idea to have module A depend on B and B depend on A. In that case it is more wise to just use one module that contains the functionality of both or change your interfaces so that B doesnt rely on A. — benebo22, Jun 10 '21 at 13:46

score 0 · Answer 1 · answered Jun 10 '21 at 13:47

0

You can use Spring bean configurations:

For example, you have a class BClass from your project B (not a Spring boot project), and you need to inject BClass in your Spring boot project A, you create a Spring configuration class/

@Configuration
public class AConfiguration {

   @Bean
   public BClass configureBClass() {
       return new BClass();
   }

}

Then you can inject BClass in your Spring boot project:

@Autowired
BClass bClass;

Don't forget to add project B as a dependency, and you should create AConfiguration class under your Spring boot main package.

answered Jun 10 '21 at 13:47

Ismail

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I have to do vice versa... Inject A project class to B project B class . – Kittu Karan Jun 10 '21 at 14:57
If B is a Spring boot project, you can do the same as mentioned. It's not recommended though, you will get a circular dependency. – Ismail Jun 10 '21 at 15:04

score 0 · Answer 2 · answered Jun 10 '21 at 14:03

If you mean that A has implementation of interfaces from B and you define your interfaces in module B, spring can autowire implementations from A in components contained in B:

//contained in A
@Component
class BookRetrievalServiceImpl implements BookRetrievalService {

    @Override
    findBookById(String id){
        //TODO do something
    }
}

//contained in B
interface BookRetrievalService {
    Book findBookById(String id);
}

//contained in B
@Component
class BookBillingService {
  private BookRetrievalService bookRetrievalService;

  // BookRetrievalServiceImpl gets autowired here. 
  public BookBillingService(BookRetrievalService bookRetrievalService){
   this.bookRetrievalService = bookRetrievalService;
  }

  public void calculateBilling(String bookId){
      //TODO retrieve book and calculate...
  }
}

score 0 · Answer 3 · answered Jun 10 '21 at 14:16

If I understood your problem, you've two projects A and B where A is dependent on B. Technically, A has a maven dependency of B so A can access all the classes of B. But if you see, B doesn't know about A. Think like you're adding a Spring artifact in your POM to use its classes, but does it mean that Spring Artifact can also access your Classes, no, right?

Another thing, you said B is kind of common module, now if you make B dependent on A, it may not remain common.

As you've not given any concrete details, I can suggest you to try with Spring Events. With Spring Events, two Siblings can interact without having a dependency of one another. See here Spring Boot Application Events Explained

Can springboot dependency class can autowire service module?

3 Answers3